Exam 2 Version 1 October 10, 2006

CHM-101-A Exam 2 Version 1 October 10, 2006

1. Which of the following statements is incorrect? A. SF4 has ¼ as many sulfur atoms as fluorine atoms. B. Ca(NO3)2 has six times as many oxygen atoms as calcium ions. C. H2SO4 has twice as many oxygen atoms as hydrogen atoms. D. SO2 has twice as many oxygen atoms as sulfur atoms. E. N2H4 has four times as many hydrogen atoms as nitrogen atoms.

2. How many oxygen atoms are there in 0.25 mole of CO2? A. 4.2 × 10-25 B. 0.25 C. 3.0 × 1023 D. 0.50 E. 1.5 × 1023

3. Rank the following in order of increasing mass: 0.50 mole of water (H2O), 0.20 mole of Fe, and 0.010 mole of U. A. U < H2O < Fe B. U < Fe < H2O C. H2O < U < Fe D. U < H2O < Fe E. H2O < Fe < U

4. A 5.05 g sample of quartz (SiO2) contains 2.36 g of silicon. What are the percents of silicon and oxygen in quartz? A. 46.7% Si, and insufficient information to calculate % O B. 53.3% Si and 46.7% O C. 46.7% Si and 53.3% O D. 29.9% Si and 70.1% O E. 70.1% Si and 29.9% O

5. Calculate the number of moles of NaOH (sodium hydroxide, an ingredient in drain cleaners and oven cleaners) in a 10.0 g sample of this substance. A. 0.250 mole B. 1.66 × 1023 mole C. 0.208 mole D. 4.00 × 102 moles E. 1.51 × 1023 moles

6. Given the following molecular formulas, determine the empirical formula of each compound: N2O5, H2O2, C6H4Cl2. A. N2O5, H2O2, C3H2Cl2 B. N2O5, HO, C3H2Cl C. N2O5, H2O, C6H4Cl2 D. N2O5, HO, C6H4Cl2 E. NO2.5, HO, C3H2Cl

7. Acetic acid is the active ingredient in vinegar. It consists of 40.00% C, 6.73% H, and 53.28% O. What is the empirical formula of acetic acid? A. CH3O B. C2H4O2 C. C3H6O3 D. CH2O E. C3.33H6.66O3.33

8. Calculate the molarity of a solution consisting of 60.0 g of NaOH in 1.50 L of solution. A. 40.0 M B. 1.50 M C. 1.60 × 103 M D. 1.00 M E. 1.74 M

9. The figure shows the chemical reaction between nitrogen gas and hydrogen gas to produce ammonia (NH3) gas. Is the diagram accurate, and if not, what is wrong with it, and how could it be fixed?

A. The nitrogen molecules would not break apart, so the image on the right should have two nitrogen atoms in each of two molecules. B. The diagram is correct as shown. C. There are not enough hydrogen atoms in the image on the right. Add another hydrogen atom to each molecule on the right. D. There are not enough hydrogen atoms in either of the two images. Add one more hydrogen molecule to the left image, and one more hydrogen atom to each molecule shown on the right. E. There are too few hydrogen atoms in the image on the left. Add one hydrogen molecule.

10. Balance the following skeletal equation: C3H8(g) + O2(g) → CO2(g) + H2O(g). A. C3H8(g) + O2(g) → 3CO2(g) + 4H2O(g) B. C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g) C. C3H8(g) + O2(g) → 3CO2(g) + 2H2O(g) D. C3H8(g) + 3O2(g) → 3CO2(g) + 4H2O(g) E. C3H8(g) + 4O2(g) → 3CO2(g) + 4H2O(g)

11. A reaction which has two elements as reactants and one compound as a product is: A. a combination reaction. B. a decomposition reaction. C. a double-displacement reaction. D. a combustion reaction. E. a single-displacement reaction.

12. A piece of magnesium metal is placed in a solution of hydrochloric acid, resulting in the formation of hydrogen gas and a solution of magnesium chloride. The class of this reaction is: A. combination reaction. B. single-displacement reaction. C. double-displacement reaction. D. decomposition reaction. E. combustion reaction.

13. The class of the reaction shown in the figure is:

A. combustion reaction. B. single-displacement reaction. C. combination reaction. D. decomposition reaction. E. double-displacement reaction.

14. When copper metal is placed in a solution of zinc nitrate, will a reaction occur? If so, what is the balanced equation for the reaction? A. Yes. Cu(s) + Zn(NO3)2(aq) → CuNO3(aq) + ZnNO3(aq) B. Yes. Cu(s) + Zn(NO3)2(aq) → Cu(NO3)2(aq) + Zn(s) C. Yes. Cu(s) + Zn2NO3(aq) → CuNO3(aq) + 2Zn(aq) D. No reaction will occur. E. Yes. Cu(s) + Zn2NO3(aq) → CuNO3(aq) + Zn(aq)

15. When aqueous solutions of sodium chloride and silver nitrate are mixed, a double- displacement reaction occurs. What is the balanced equation for the reaction? A. NaCl(aq) + AgNO3(aq) → NaNO3(aq) + AgCl(aq) B. NaCl(aq) + AgNO3(aq) → NaNO3(aq) + 3AgCl(s) C. NaCl(aq) + AgNO3(aq) → NaNO3(aq) + Ag(s) + Cl(g) D. NaCl(aq) + AgNO3(aq) → NaNO3(aq) + AgCl(s) E. NaCl(aq) + AgNO3(aq) → Na(s) + AgNO3Cl(aq)

16. Which of the following ionic compounds would be expected to be insoluble in water? A. PbI2 B. KCl C. NH4NO3 D. NaCH3CO2 E. CuSO4

17. Write and balance a net ionic equation for the reaction between iron(II) chloride and potassium hydroxide to form iron(II) hydroxide and potassium chloride. 2+ - A. Fe (aq) + 2OH (aq) → Fe(OH)2(s) B. 2Cl-(aq) + 2K+(aq) → 2KCl(s) C. Fe2+(aq) + OH-(aq) → FeOH(s) - + D. 2Cl (aq) + 2K (aq) → 2K(s) + Cl2(g) - - E. Fe2Cl(aq) + OH (aq) → FeOH(s) + Cl (aq)

18. Which of the following is the best (simplest) balanced equation to represent the chemical reaction shown in the figure on any scale?

A. 8H2 + 5O2 → 8H2O + O2 B. 4H2 + 2O2 → 4H2O C. 2H2 + O2 → 2H2O D. 16H + 10O → 8H2O + O2 E. 16H + 10O → 16H + 10O

19. When mixed, solutions of aluminum nitrate, Al(NO3)3, and ammonium carbonate, (NH4)2CO3, will form a precipitate of aluminum carbonate, Al2(CO3)3. The balanced equation is: 2Al(NO3)3(aq) + 3(NH4)2CO3(aq)→ Al2(CO3)3(s) + 6NH4NO3(aq) Which of the following statements regarding this reaction is incorrect? A. If 6 moles of (NH4)2CO3 react with sufficient Al(NO3)3, 2 moles of Al2(CO3)3 will be formed. B. 2 moles of Al(NO3)3 will react with 3 moles of (NH4)2CO3. C. If 0.5 mole of (NH4)2CO3 react with sufficient Al(NO3)3, 3 moles of Al2(CO3)3 will be formed. D. 4 moles of Al(NO3)3 will react with 6 moles of (NH4)2CO3. E. If 1.5 moles of Al2(CO3)3 are formed, given sufficient starting materials, then 9 moles of NH4NO3 will also be formed.

20. Phosphine, PH3, a reactive and poisonous compound, reacts with oxygen as follows: 4PH3(g) + 8O2(g)→ P4O10(s) + 6H2O(g) If 9.2 moles of phosphine react with sufficient oxygen, how many moles of P4O10 will be formed? A. 9.2 moles B. 2.3 moles C. 37 moles D. 6.0 moles E. 4.0 moles

21. Phosphorus trichloride can be made by the reaction: P4(s) + 6Cl2(g) → 4PCl3(l) What is the maximum amount of phosphorus trichloride that can be formed if 10 molecules of P4 react with 36 molecules of chlorine? A. 4 molecules B. 12 molecules C. 24 molecules D. 46 molecules E. 6 molecules

22. The figure shows a molecular-level diagram of reactant molecules for the reaction: 2H2(g) + O2(g) → 2H2O(l)

List the number and formulas of the molecules that will be present after the reaction takes place. A. 4H2O, 4H2, O2 B. 2H2O, 6H2, 2O2 C. 3H2O, 5H2, O2 D. 6H2O, 2H2 E. 6H2O, 2H2, O2

23. In the process of obtaining lead from PbS, or galena, the galena is "roasted" (heated in the presence of oxygen), so that the following reaction occurs: 2PbS(s) + 3O2(g) → 2PbO(s) + 2SO2(g) If 50.0 g of PbS reacts with 25.0 g of oxygen, how many grams of PbO will be formed? A. 69.9 g B. 163 g C. 116 g D. 93.2 g E. 46.6 g

24. Which of the following processes is exothermic? A. dry ice (solid CO2) converting to a gas at room temperature B. evaporation of water from a mud puddle C. ice melting in a beverage D. wax melting on the top of a burning candle E. burning propane in a barbeque grill

25. If 75.0 J of heat energy are added to separate 25.0 g samples of aluminum (C = 0.895 J/goC), chromium (C = 0.450 J/goC), and copper (C = 0.377 J/goC), rank the metals in order from least to greatest final temperature. A. Al < Cu < Cr B. Cr < Cu < Al C. none of these—all final temperatures would be equal D. Cu < Cr < Al E. Al < Cr < Cu

Exam 2 Version 1 Key

1. E 2. C 3. A or D 4. C 5. A 6. B 7. D 8. D 9. E 10. B 11. A 12. B 13. D 14. D 15. D 16. A 17. A 18. C 19. C 20. B 21. C 22. D 23. E 24. E 25. E

1. Which of the following statements is incorrect? A. SO2 has twice as many oxygen atoms as sulfur atoms. B. N2H4 has four times as many hydrogen atoms as nitrogen atoms. C. H2SO4 has twice as many oxygen atoms as hydrogen atoms. D. SF4 has ¼ as many sulfur atoms as fluorine atoms. E. Ca(NO3)2 has six times as many oxygen atoms as calcium ions.

2. How many oxygen atoms are there in 0.25 mole of CO2? A. 1.5 × 1023 B. 0.50 C. 0.25 D. 4.2 × 10-25 E. 3.0 × 1023

3. Rank the following in order of increasing mass: 0.50 mole of water (H2O), 0.20 mole of Fe, and 0.010 mole of U. A. H2O < Fe < U B. U < H2O < Fe C. U < H2O < Fe D. H2O < U < Fe E. U < Fe < H2O

4. A 5.05 g sample of quartz (SiO2) contains 2.36 g of silicon. What are the percents of silicon and oxygen in quartz? A. 29.9% Si and 70.1% O B. 53.3% Si and 46.7% O C. 46.7% Si, and insufficient information to calculate % O D. 46.7% Si and 53.3% O E. 70.1% Si and 29.9% O

5. Calculate the number of moles of NaOH (sodium hydroxide, an ingredient in drain cleaners and oven cleaners) in a 10.0 g sample of this substance. A. 0.208 mole B. 0.250 mole C. 1.66 × 1023 mole D. 4.00 × 102 moles E. 1.51 × 1023 moles

6. Given the following molecular formulas, determine the empirical formula of each compound: N2O5, H2O2, C6H4Cl2. A. N2O5, H2O, C6H4Cl2 B. N2O5, H2O2, C3H2Cl2 C. NO2.5, HO, C3H2Cl D. N2O5, HO, C6H4Cl2 E. N2O5, HO, C3H2Cl

7. Acetic acid is the active ingredient in vinegar. It consists of 40.00% C, 6.73% H, and 53.28% O. What is the empirical formula of acetic acid? A. C3.33H6.66O3.33 B. C3H6O3 C. C2H4O2 D. CH2O E. CH3O

8. Calculate the molarity of a solution consisting of 60.0 g of NaOH in 1.50 L of solution. A. 1.50 M B. 1.60 × 103 M C. 40.0 M D. 1.00 M E. 1.74 M

9. The figure shows the chemical reaction between nitrogen gas and hydrogen gas to produce ammonia (NH3) gas. Is the diagram accurate, and if not, what is wrong with it, and how could it be fixed?

A. There are too few hydrogen atoms in the image on the left. Add one hydrogen molecule. B. There are not enough hydrogen atoms in the image on the right. Add another hydrogen atom to each molecule on the right. C. The diagram is correct as shown. D. There are not enough hydrogen atoms in either of the two images. Add one more hydrogen molecule to the left image, and one more hydrogen atom to each molecule shown on the right. E. The nitrogen molecules would not break apart, so the image on the right should have two nitrogen atoms in each of two molecules.

10. Balance the following skeletal equation: C3H8(g) + O2(g) → CO2(g) + H2O(g). A. C3H8(g) + 3O2(g) → 3CO2(g) + 4H2O(g) B. C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g) C. C3H8(g) + O2(g) → 3CO2(g) + 4H2O(g) D. C3H8(g) + O2(g) → 3CO2(g) + 2H2O(g) E. C3H8(g) + 4O2(g) → 3CO2(g) + 4H2O(g)

11. A reaction which has two elements as reactants and one compound as a product is: A. a combination reaction. B. a single-displacement reaction. C. a combustion reaction. D. a double-displacement reaction. E. a decomposition reaction.

12. A piece of magnesium metal is placed in a solution of hydrochloric acid, resulting in the formation of hydrogen gas and a solution of magnesium chloride. The class of this reaction is: A. decomposition reaction. B. double-displacement reaction. C. single-displacement reaction. D. combustion reaction. E. combination reaction.

13. The class of the reaction shown in the figure is:

A. double-displacement reaction. B. single-displacement reaction. C. decomposition reaction. D. combustion reaction. E. combination reaction.

14. When copper metal is placed in a solution of zinc nitrate, will a reaction occur? If so, what is the balanced equation for the reaction? A. Yes. Cu(s) + Zn(NO3)2(aq) → CuNO3(aq) + ZnNO3(aq) B. Yes. Cu(s) + Zn2NO3(aq) → CuNO3(aq) + Zn(aq) C. Yes. Cu(s) + Zn2NO3(aq) → CuNO3(aq) + 2Zn(aq) D. Yes. Cu(s) + Zn(NO3)2(aq) → Cu(NO3)2(aq) + Zn(s) E. No reaction will occur.

15. When aqueous solutions of sodium chloride and silver nitrate are mixed, a double- displacement reaction occurs. What is the balanced equation for the reaction? A. NaCl(aq) + AgNO3(aq) → NaNO3(aq) + AgCl(s) B. NaCl(aq) + AgNO3(aq) → Na(s) + AgNO3Cl(aq) C. NaCl(aq) + AgNO3(aq) → NaNO3(aq) + 3AgCl(s) D. NaCl(aq) + AgNO3(aq) → NaNO3(aq) + Ag(s) + Cl(g) E. NaCl(aq) + AgNO3(aq) → NaNO3(aq) + AgCl(aq)

16. Which of the following ionic compounds would be expected to be insoluble in water? A. KCl B. NH4NO3 C. NaCH3CO2 D. PbI2 E. CuSO4

17. Write and balance a net ionic equation for the reaction between iron(II) chloride and potassium hydroxide to form iron(II) hydroxide and potassium chloride. - - A. Fe2Cl(aq) + OH (aq) → FeOH(s) + Cl (aq) 2+ - B. Fe (aq) + 2OH (aq) → Fe(OH)2(s) C. Fe2+(aq) + OH-(aq) → FeOH(s) - + D. 2Cl (aq) + 2K (aq) → 2K(s) + Cl2(g) E. 2Cl-(aq) + 2K+(aq) → 2KCl(s)

18. Which of the following is the best (simplest) balanced equation to represent the chemical reaction shown in the figure on any scale?

A. 2H2 + O2 → 2H2O B. 8H2 + 5O2 → 8H2O + O2 C. 4H2 + 2O2 → 4H2O D. 16H + 10O → 8H2O + O2 E. 16H + 10O → 16H + 10O

19. When mixed, solutions of aluminum nitrate, Al(NO3)3, and ammonium carbonate, (NH4)2CO3, will form a precipitate of aluminum carbonate, Al2(CO3)3. The balanced equation is: 2Al(NO3)3(aq) + 3(NH4)2CO3(aq)→ Al2(CO3)3(s) + 6NH4NO3(aq) Which of the following statements regarding this reaction is incorrect? A. If 0.5 mole of (NH4)2CO3 react with sufficient Al(NO3)3, 3 moles of Al2(CO3)3 will be formed. B. If 1.5 moles of Al2(CO3)3 are formed, given sufficient starting materials, then 9 moles of NH4NO3 will also be formed. C. If 6 moles of (NH4)2CO3 react with sufficient Al(NO3)3, 2 moles of Al2(CO3)3 will be formed. D. 2 moles of Al(NO3)3 will react with 3 moles of (NH4)2CO3. E. 4 moles of Al(NO3)3 will react with 6 moles of (NH4)2CO3.

20. Phosphine, PH3, a reactive and poisonous compound, reacts with oxygen as follows: 4PH3(g) + 8O2(g)→ P4O10(s) + 6H2O(g) If 9.2 moles of phosphine react with sufficient oxygen, how many moles of P4O10 will be formed? A. 6.0 moles B. 9.2 moles C. 4.0 moles D. 37 moles E. 2.3 moles

21. Phosphorus trichloride can be made by the reaction: P4(s) + 6Cl2(g) → 4PCl3(l) What is the maximum amount of phosphorus trichloride that can be formed if 10 molecules of P4 react with 36 molecules of chlorine? A. 6 molecules B. 46 molecules C. 24 molecules D. 4 molecules E. 12 molecules

22. The figure shows a molecular-level diagram of reactant molecules for the reaction: 2H2(g) + O2(g) → 2H2O(l)

List the number and formulas of the molecules that will be present after the reaction takes place. A. 2H2O, 6H2, 2O2 B. 6H2O, 2H2, O2 C. 3H2O, 5H2, O2 D. 4H2O, 4H2, O2 E. 6H2O, 2H2 Copyright 2006 by James P. Birk 5 CHM-101-A Exam 2 Version 2 October 10, 2006

24. Which of the following processes is exothermic? A. dry ice (solid CO2) converting to a gas at room temperature B. wax melting on the top of a burning candle C. ice melting in a beverage D. burning propane in a barbeque grill E. evaporation of water from a mud puddle

25. If 75.0 J of heat energy are added to separate 25.0 g samples of aluminum (C = 0.895 J/goC), chromium (C = 0.450 J/goC), and copper (C = 0.377 J/goC), rank the metals in order from least to greatest final temperature. A. Al < Cr < Cu B. none of these—all final temperatures would be equal C. Cu < Cr < Al D. Cr < Cu < A E. Al < Cu < Cr

Exam 2 Version 2 Key

1. B 2. E 3. C or B 4. D 5. B 6. E 7. D 8. D 9. A 10. B 11. A 12. C 13. C 14. E 15. A 16. D 17. B 18. A 19. A 20. E 21. C 22. E 23. B 24. D 25. A